<a href=showthread.php?s=&postid=9547028#post9547028 target=_blank>Originally posted</a> by IslandCrow
You probably won't want to put the powerhead too close to the sand, or you're going to get a serious sand storm. Initially, especially if you're using really fine sand, you'll probably want to keep your powerheads towards the top of the tank and not pointed down at all. After awhile, your sand will start to bind together, and it won't be as much of an issue. You do want some flow along the bottom of your tank for just the reason you stated, though. Generally, the best thing to do is keep the powerheads towards the top of the tank, perhaps pointed slightly down, and use at least two powerheads with their streams crossing each other. This is going to disperse the flow and make it more random. If you're planning on doing corals, they'll love you for it.
Oh, and if your powerheads come with suction cups, don't use them. They're going to lose their suction before long, and you're going to have a rogue powerhead spinning around your tank causing all sorts of havoc.